1. Field of the Invention
The present invention relates to a slush hydrogen production apparatus adapted to produce slush hydrogen including solid hydrogen and liquid hydrogen coexisting with each other.
2. Description of the Prior Art
Conventionally, as the principles of producing such slush hydrogen the following methods are presented as achievements of scientific studies in the international conferences of the cryogenic engineering society or in the 8th world hydrogen energy conference held in Hawaii, 1990. That is, they are an indirect cooling method in which liquid helium is supplied into a cooling jacket of a container containing liquid hydrogen, so as to flow therethrough and to produce solid hydrogen frozen on the inner wall of the container and then the solid hydrogen is scraped off by means of a screw, a direct cooling method in which low-temperature gaseous helium is blown into liquid hydrogen through a helium supply tube so as to produce solid hydrogen at the leading end of the tube, a continuous pressure reduction method in which by supplying liquid hydrogen into a closed container and decreasing a pressure within the closed container not more than its triple point pressure a solid layer of the hydrogen is produced in the surface of the liquid hydrogen, and an intermittent pressure reduction method in which after the solid layer of the hydrogen has been produced on the surface of the liquid hydrogen by decreasing the pressure within the closed container not more than the triple point pressure, the pressure therewithin is increased above the triple point pressure so as to dissolve such portions of the surface solid layer that are in contact with the inner wall surface of the container to sink the solid layer. However, such an apparatus as to enable an efficient mass production of the slush hydrogen by an industrial procedure has not been developed yet.
In the case of the slush hydrogen production by means of the indirect cooling method, since the solid hydrogen frozen on the inner wall of the container is scraped off by means of the screw, there is such a problem that a clearance setting between the inner wall on which the solid hydrogen is produced and the scraping screw is too delicate to even the particle diameters of the solid hydrogen.
In the case of the slush hydrogen production by means of the direct cooling method, since the solid hydrogen is produced at the leading end of the helium supply tube by blowing the low-temperature gaseous helium into the liquid hydrogen, the solid hydrogen to be produced thereat is apt to grow along the flowing direction of the gaseous helium in a tubular manner. Therefore, it is necessary to break the tubular grown solid hydrogen by means of stirs. Also in this case, there is such a problem that uniformalization of the solid particle diameters becomes difficult.
In the case of the slush hydrogen production by means of the continuous pressure reduction method, since the liquid hydrogen is supplied into the closed container and then the pressure within the closed container is decreased not more than the triple point pressure so as to produce the solid layer of the hydrogen in the liquid surface portion, the solid hydrogen is apt to be produced from such a portion of the liquid layer that is in contact with the gas phase as well as from the portions thereof being in contact with the inner peripheral wall of the container. Therefore, though the stirring operation is carried out in the liquid phase portion, it is hard to break the solid layer because the solid layer has been formed along the peripheral wall. There is also such a problem that it is difficult to produce the slush hydrogen throughout the interior of the closed container.
On the one hand, in the case of the slush hydrogen production by means of the intermittent pressure reduction method, since the portion of the frozen solid hydrogen along the container peripheral wall is dissolved by periodically changing over the pressure within the closed container to a pressure not more than the triple point and to a pressure above the triple point so that the solid layer produced on the liquid surface can sink in the liquid due to density difference therebetween, the generation and growth of the solid layer can be enhanced by exposing the liquid surface to the gas phase every certain time (from several seconds to ten and several seconds). But, in this case, since the solid hydrogens are merely sunk into the liquid, there is such a problem that it is difficult to even the diameters of the solid particles in the liquid.
That is, by means of the conventional slush hydrogen production apparatus, it is possible to produce the slush hydrogen but it is difficult to produce such slush hydrogen that includes solid particles of uniform diameters. As a result, it is too long before practical applications of those apparatus. Further, the slush hydrogen production apparatus previously presented in the conference are merely directed mainly to producing the slush hydrogen but a supply of the liquid hydrogen as a raw material and a removal of the slush hydrogen are not considered in these apparatuses.
The present invention is directed to solving such problems, and it is an object of the present invention to provide a slush hydrogen production apparatus which is capable of efficiently producing the slush hydrogen including solid particles of uniform diameters by means of an industrial procedure.